A Study Of The Drag Characteristics And Polymer Diffusion In The Boundary Layer Of An Axisymmetric Body

Drag reduction by ejection of high molecular weight polymers on free-running bodies of revolution has been demonstrated repeatedly. The quantities of polymer required have made the gains achieved marginal from a volume utilization tradeoff. The ejection process is hypothesized to be the controlling factor. Limited data obtained in pipe flow and flat plate flow experiments on ejection into developing boundary layers indicate a drastic reduction in polymer requirements for equivalent percent drag reductions. Extension to axisymmetric flow could result in significant achievable gains to volume utilization. This study examines these polymer ejection processes through measurement of wall and boundary layer concentration profiles and through a photographic study of the boundary layer. Tests performed with fresh water ejection and solutions of the drag reducing polymer, Polyox WSR-301, lead to the hypothesis that optimal ejection for minimum polymer usage requires ejection into a laminar boundary layer prior to turbulent flow transition. Analytical routines are developed which predict boundary layer parameters and polymer wall concentrations for this postulated optimal ejection process or the suboptimal case. Limited verification of the model is made. (Author).

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Drag reduction by injection of high molecular weight polymers into boundary layers has been demonstrated repeatedly in the past. However, from a volume utilization tradeoff standpoint, the quantities of polymer required make the gains achieved by this process marginal. While indicating reduced polymer requirements for drag reduction, limited data obtained from pipe flow and external boundary layer flow experiments are conflicting and hard to interpret. Ambiguities in measurement techniques due to polymer effects on commonly used instrumentation and opposing features of varied flow facilities have also contributed to making these earlier works contradictory and difficult to resolve. Experiments performed in this research indicate that turbulence intensity distributions are altered by the addition of polymer in such a way that the peak of turbulence production is lowered and its location moved away from the wall. The transition region is delayed and extended by the addition of polymer to the boundary layer. The laminar sublayer of boundary layer profiles appears to have thickened due to the addition of polymer. When compared to the law of the wall corrected for developing flow, the velocity profiles also show evidence of a thickened sublayer.

Contains papers from a February 1996 seminar on magnetohydrodynamic (MHD) flows and turbulence, covering contemporary trends in both experimental and theoretical research and presenting recent results in many areas. Subjects include transition, turbulence, MHD and atmospheric turbulence, astrophysics, experimental methods and data analysis, energy conversion, solidification, incompressible flow, and plasma MHD. Some topics are structure of the velocity field of a turbulent line-fire plume, helical instability of magnetohydrodynamic turbulence, energy sources of planetary magnetic fields, and characterization of microfabricated shear stress sensors. No index. Annotation copyrighted by Book News, Inc., Portland, OR